1. Field of the Invention
The present invention relates to a medical image processing device for generating an image in which the difference in color between a normal part and a lesion part is enhanced, an operation method therefor, and an endoscope system.
2. Description of the Related Art
In a medical field, diagnosis using an endoscope system comprising a light source device, an endoscope, and a processor device has been widely performed. In this endoscope system, an observation target is irradiated with illumination light from the endoscope, and an image of the observation target is displayed on a monitor based on an image signal obtained by imaging the observation target being irradiated with illumination light with an imaging element of the endoscope. A doctor detects the presence or absence of a lesion part while viewing the image displayed on the monitor.
It is possible to easily detect a lesion part, such as a lesion part significantly protruding from a mucosal surface, which is significantly different in shape or size from a normal part. However, a lesion part which is nearly the same in shape or size as a normal part is detected based on a difference in color from the normal part. In this case, it is extremely difficult to detect a lesion part in a case where the lesion part has not progressed and the color thereof is nearly the same as that of the normal part.
Accordingly, in JP3228627B (corresponding to U.S. Pat. No. 5,550,582 and U.S. Pat. No. 5,675,378), the difference in color between a normal part and a lesion part is made distinct by processing a part where a value of a blood volume (hemoglobin index) is distant from a reference value such that the value of the blood volume becomes more distant from the reference value.
It is known that, in a case of a gastric cancer among the lesion parts, a gastric mucosa is atrophied and the gastric mucosa is faded. For this reason, an atrophic part where atrophy occurs in a mucosa is different in color from a normal part where atrophy does not occur. The presence or absence of a gastric cancer is diagnosed by observing the difference in color from the normal part with the endoscope (there is an ABC examination which is recommended by Certified NPO: Japan Research Foundation of Prediction, Diagnosis and Therapy for Gastric Cancer).
In a case where atrophy has progressed to a high degree (for example, in a case where atrophy is included in a group C or a group D in the ABC examination), since the difference in color between a normal part and an atrophic part is distinct, it is possible to easily detect the atrophic part. However, in a case where atrophy is progressing (for example, in a case where atrophy is included in a group B or a group C in the ABC examination), since the difference in color between an atrophic part and a normal part is slight, it is difficult to detect an atrophic part only with the difference in color. Accordingly, there is demand for easy detection of an atrophic part by enhancing the difference in color between a normal part and an atrophic part even in a case where the difference in color between an atrophic part and a normal part is slight as when in the event that atrophy is progressing.
It is considered that the difference in color between an atrophic part and a normal part is enhanced by the method of JP3228627B. However, since the color of the atrophic part is affected by not only the blood volume but also elements other than the blood volume, in the method of JP3228627B, it is difficult to enhance the difference in color between an atrophic part and a normal part.